This invention relates to a glucose-repressible gene and more particularly to a regulatory region from that gene.
Glucose is the preferred source of carbon and energy for cellular growth. Glucose repression, is a well-known phenomenon in which the presence of glucose in the medium represses the expression of a number of genes (glucose-repressible genes). Glucose repression is an important regulatory system present in virtually all cells and is well defined in certain prokaryotic cells such as E. coli.
A regulatory region from a glucose-repressible gene may also have wide application. The use of a regulatory region to confer high level expression upon a recombinant DNA sequence coding for a desired protein would allow efficient production of the protein.
In the filamentous fungi, a number of enzymatic activities are expressed (derepressed) whenever glucose is limiting. These glucose-repressible activities allow the fungi to utilize alternate carbon and energy sources. Therefore, for example, fungal cells containing a recombinant DNA molecule encoding a desired protein could be grown in a glucose medium and during the exponential growth phase the desired protein would not be produced. As the cells reach the end of the growth phase the glucose would be depleted and the desired protein would be synthesized at high levels. This type of system has the advantage of not producing the protein during the growth phase, when it's presence might be deleterious to the fungus. However, large amounts of the protein may be produced during the late phases of growth, when there is a large number of cells.
The use of filamentous fungi to synthesize protein products would have the advantage that fungal cells will proteolytically process (cleave with proteases) the protein in the same manner as human cells. The process of adding carbohydrates, a process common in human cells, occurs in a similar fashion within the filamentous fungi. In order to produce a protein having normal biological activity in eukaryotic organisms these two processes (the proteolytic processing of the protein and the addition of carbohydrates) must occur. The filamentous fungi are easy to cultivate and have been used in industrial applications. For these reasons, a filamentous fungi which can effectively be used for industrial production of proteins is desirable.
Unfortunately, to date no such regulatory region has been used in chimeric form to allow the accomplishment of the above objectives.